Magnetic field sensing element and device having magnetoresistance element and integrated circuit formed on the same substrate

ABSTRACT

A magnetic field sensing element comprises an underlayer formed on a substrate, a giant magnetoresistance element formed on the underlayer for detecting a change in a magnetic field, and an integrated circuit formed on the substrate for carrying out predetermined arithmetic processing based on a change in a magnetic field detected by the giant magnetoresistance element, wherein the giant magnetoresistance element and the integrated circuit are formed on the same surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic field sensing element fordetecting a change in a magnetic field, and more particularly, such anelement used in a device for detecting the rotation of a magnetic body.

2. Description of the Related Art

Generally, a magnetoresistance element (hereinafter referred to as an MRelement) is an element whose resistance changes depending on an angleformed by the direction of magnetization of a ferromagnetic body (Ni—Feor Ni—Co, for example) thin film and the direction of an electriccurrent. The resistance of such an MR element is minimum when thedirection of an electric current and the direction of magnetizationcross at right angles to each other, and is maximum when the angleformed by the direction of an electric current and the direction ofmagnetization is 0°, that is, when the directions are the same orcompletely opposite. Such a change in resistance is referred to as an MRratio, and is typically 2—3% with respect to Ni—Fe and 5—6% with respectto Ni—Co.

FIGS. 34 and 35 are a side view and a perspective view, respectively,showing the structure of a conventional magnetic field sensing device.

As shown in FIG. 34, the conventional magnetic field sensing devicecomprises a rotation axis 41, a magnetic rotating body 42 which has atleast one concavity and convexity and which rotates synchronously withthe rotation of the rotation axis 41, an MR element 43 arranged with apredetermined gap between itself and the magnetic rotating body 42, amagnet 44 for applying a magnetic field to the MR element 43, and anintegrated circuit 45 for processing an output of the MR element 43. TheMR element 43 has a magnetoresistance pattern 46 and a thin film surface(magnetic-sensitive surface) 47.

In such a magnetic field sensing device, rotation of the magneticrotating body 42 causes a change in the magnetic field penetrating thethin film surface 47 which is the magnetic-sensitive surface of the MRelement 43, resulting in a change in the resistance of themagnetoresistance pattern 46.

However, since the output level of the MR element as a magnetic fieldsensing element used in such a magnetic field sensing device is low, thedetection can not be highly accurate. In order to solve this problem, amagnetic field sensing element using a giant magnetoresistance element(hereinafter referred to as a GMR element) having a high output levelhas been recently proposed.

FIG. 36 is a graph showing the characteristics of a conventional GMRelement.

The GMR element showing the characteristics in FIG. 36 is a laminatedbody (Fe/Cr, permalloy/Cu/Co/Cu, Co/Cu, FeCo/Cu) as a so-calledartificial lattice film where magnetic layers and non-magnetic layerswith thickness of several angstroms to several dozen angstroms arealternately laminated. This is disclosed in an article entitled“Magnetoresistance Effects of Artificial Lattices,” Japan AppliedMagnetics Society Transactions, Vol. 15, No. 51991, pp. 813—821. Thelaminated body has a much larger MR effect (MR ratio) than theabove-mentioned MR element, and, at the same time, is an element whichshows the same change in resistance irrespective of the angle formed bythe direction of an external magnetic field and the direction of anelectric current.

In order to detect a change in the magnetic field, the GMR elementsubstantially forms a magnetic-sensitive surface. Electrodes are formedat the respective ends of the magneticsensitive surface to form a bridgecircuit. A constant-voltage and constant-current power source isconnected between the two facing electrodes of the bridge circuit. Thechange in the magnetic field acting on the GMR element is detected byconverting a change in the resistance of the GMR element into a changein voltage.

FIGS. 37 and 38 are a side view and a perspective view, respectively,showing the structure of a magnetic field sensing device using aconventional GMR element.

In FIGS. 37 and 38, the magnetic field sensing device comprises arotation axis 41, a magnetic rotating body 42 as a means for imparting achange to a magnetic field, the body having at least one concavity andconvexity and having rotatable synchronously with the rotation of therotation axis 41, a GMR element 48 arranged with a predetermined gapbetween the magnetic rotating body 42, a magnet 44 as a magnetic fieldgenerating means for applying a magnetic field to the GMR element 48,and an integrated circuit 45 for processing an output of the GMR element48. The GMR element 48 has a magnetoresistance pattern 49 as amagnetic-sensitive pattern and a thin film surface 50.

In such a magnetic field sensing device, rotation of the magneticrotating body 42 causes a change in the magnetic field penetrating thethin film surface (magnetic-sensitive surface) 47 of the GMR element 48,resulting in a change in the resistance of the magnetoresistance pattern49.

FIG. 39 is a block diagram showing the magnetic field sensing deviceusing the conventional GMR element.

FIG. 40 is a block diagram showing the detail of the magnetic fieldsensing device using the conventional GMR element.

The magnetic field sensing device shown in FIGS. 39 and 40 is arrangedwith a predetermined gap between the magnetic rotating body 42 anditself, and comprises a Wheatstone bridge circuit 51 using the GMRelement 48 to which a magnetic field is applied by the magnet 44, adifferential amplification circuit 52 for amplifying the output of theWheatstone bridge circuit 51, a comparison circuit 53 for comparing theoutput of the differential amplification circuit 52 with a referencevalue to output a signal of either “0” or “1,” and an output circuit 54that switches in response to the output of the comparison circuit 53.

FIG. 41 shows an example of the structure of a circuit of the magneticfield sensing device using the conventional GMR element.

In FIG. 41, the Wheatstone bridge circuit 51 has on its respective sidesGMR elements 48 a, 48 b, 48 c, and 48 d, for example, with the GMRelements 48 a and 48 c being connected with a power source terminal VCC,the GMR elements 48 and 48 d being polished, the other ends of the GMRelements 48 a and 48 b being connected with a connection 55, and theother ends of the GMR elements 48 c and 48 d being connected with aconnection 56.

The connection 55 of the Wheatstone bridge circuit 51 is connected withan inverting input terminal of an amplifier 59 of a differentialamplification circuit 58 via a resistor 57. The connection 56 isconnected with a non-inverting input terminal of the amplifier 59 via aresistor 60, and is further connected with a voltage dividing circuit 62for forming a reference voltage based on the voltage supplied from thepower source terminal VCC via a resistor 61.

An output terminal of the amplifier 59 is connected with its owninverting input terminal via a resistor 63, and is further connectedwith an inverting input terminal of a comparison circuit 64. Anon-inverting input terminal of the comparison circuit 64 is connectedwith a voltage dividing circuit 66 for forming a reference voltage basedon the voltage supplied from the power source terminal VCC, and isfurther connected with an output terminal of the comparison circuit 64via a resistor 67.

An output end of the comparison circuit 64 is connected with a base of atransistor 69 of an output circuit 68. The collector of the transistor69 is connected with an output terminal of the output circuit 68 and isfurther connected with the power source terminal VCC via a resistor 71.The emitter of the transistor 69 is polished.

FIG. 42 shows the structure of the conventional magnetic field sensingelement.

FIG. 43 is a graph showing operating characteristics of the conventionalmagnetic field sensing element.

As shown in FIG. 42, the Wheatstone bridge comprises the GMR element 48(formed of 48 a, 48 b, 48 c, and 48 d).

As shown in FIG. 43, rotation of the magnetic rotating body 42 causes achange in the magnetic field supplied to the GMR element 48 (48 a to 48d), and output corresponding to the concavities and the convexities ofthe magnetic rotating body 42 can be obtained at an output end of thedifferential amplification circuit 58.

The output of the differential amplification circuit 58 is supplied tothe comparison circuit 64, compared with the reference value as thecomparison level, and converted into a signal of either “0” or “1,” andthe signal is further made into a waveform by the output circuit 68. Asa result, as shown in FIG. 43, an output of “0” or “1” with steepleading and trailing edges can be obtained at the output terminal 70.

However, since the GMR element used in the above-mentioned magneticfield sensing element is very sensitive, it is necessary to, forexample, smooth the surface of the underlayer on which the GMR elementis formed in order to fully bring out its characteristics. Therefore, itis difficult to, for example, form the GMR element on the same surfacethe integrated circuit is formed.

This makes it necessary to separately form the GMR element and theintegrated circuit and then electrically connect them with each other,which leads to low productivity and high manufacturing costs.

Further, since the output of the comparison circuit depends on the gapbetween the magnetic rotating body and the magnetic field sensingelement, there is a problem in that the so-called gap characteristicsare bad.

SUMMARY OF THE INVENTION

The present invention is made to solve the problems mentioned above, andtherefore an object of the present invention is to provide a magneticfield sensing element with low cost, high productivity, and highdetection accuracy, and a magnetic field sensing device using themagnetic field sensing element.

According to an aspect of the present invention, there is provided amagnetic field sensing element comprising, an underlayer formed on asubstrate, a giant magnetoresistance element formed on the underlayerfor detecting a change in a magnetic field, and an integrated circuitformed on the underlayer for carrying out predetermined arithmeticprocessing based on a change in a magnetic field detected by the giantmagnetoresistance element, wherein the giant magnetoresistance elementand the integrated circuit are formed on the same surface.

In a preferred form of the invention, a metal film formed on theunderlayer for forming the integrated circuit, which is not in a regionfor forming the integrated circuit, is patterned to form first wiringfor connecting the giant magnetoresistance element and the integratedcircuit.

In accordance with another aspect of the present invention, the firstwiring are formed by wet etching of the metal film and has a taperedshape in section.

In accordance with a further aspect of the present invention, a firstlevel difference buffer layer is formed on the underlayer in a regionfor forming the giant magnetoresistance element to decrease a differencein the levels between the surface of the metal film for forming thefirst wiring and a surface for forming the giant magnetoresistanceelement, and the giant magnetoresistance element is formed on the firstlevel difference buffer layer.

In a further preferred form of the invention, the first level differencebuffer layer is formed of an insulating layer, and the level differencebetween the first level difference buffer layer and the surface of themetal film for forming the first wiring is sufficiently smaller than thefilm thickness of the giant magnetoresistance element.

In a still further preferred form of the invention, the first leveldifference buffer layer is a resist layer or resin layer having fluidcharacteristics formed by spin coating, and the level difference betweenthe first level difference buffer layer and the surface of the metalfilm for forming the first wiring is sufficiently smaller than the filmthickness of the giant magnetoresistance element.

In accordance with a still further aspect of the invention, for thepurpose of forming the giant magnetoresistance element, after a giantmagnetoresistance element film is formed on the entire surface of theintegrated circuit and the first wiring, a portion of the giantmagnetoresistance element film on the first wiring then being removed sothat the giant magnetoresistance element film formed on the integratedcircuit is left unremoved, a protective film then being formed on theunremoved portion of giant magnetoresistance element film.

In accordance with a yet further aspect of the invention, there isprovided a magnetic field sensing element comprising, an integratedcircuit, an underlayer, and a metal pad formed on a substrate in theorder stated, provided with, a second level difference buffer layerformed on the underlayer and the metal pad to absorb the leveldifference between the surface of the underlayer and the surface of themetal pad, and a giant magnetoresistance element formed on the secondlevel difference buffer layer.

In a further preferred form of the invention, the second leveldifference buffer layer has a surface that is smoothed by polishing, andthe giant magnetoresistance element is formed on the smoothed surface ofthe second level difference buffer layer.

In a further preferred form of the invention, the second leveldifference buffer layer is a resist layer or resin layer having asmoothed surface formed by spin coating and the giant magnetoresistanceelement is formed on the smoothed surface of the smoothed resist layeror resin layer.

In accordance with a yet further aspect of the invention, there isprovided a magnetic field sensing element comprising an underlayerformed on one surface of a substrate, a giant magnetoresistance elementformed on the underlayer, for detecting a change in a magnetic field,and an integrated circuit formed on the surface opposite to the surfacewhere the giant magnetoresistance element of the substrate is formed,for carrying out predetermined arithmetic processing based on a changein a magnetic field detected by the giant magnetoresistance element.

In a further preferred form of the invention, an underlayer and a giantmagnetoresistance element are further formed on the integrated circuitformed on the other surface of the substrate.

In a further preferred form of the present invention, a film, which isidentical with the film composing the giant magnetoresistance element,is formed on the first wiring.

In a further preferred form of the present invention, more than half ofthe top surface and the side surface of the first wiring is coated withthe same film that forms the giant magnetoresistance element.

In accordance with a yet further aspect of the present invention, thereis provided a magnetic field sensing element comprising an integratedcircuit formed on a substrate and having a capasitor portion, anunderlayer formed on the integrated circuit, a second metal layer formedon the underlayer, and a giant magnetoresistance element formed on thecapacitor portion of the integrated circuit.

In a further preferred form of the present invention, the giantmagnetoresistance element is connected with the integrated circuitthrough second wiring formed by patterning the second metal layer.

In a further preferred form of the present invention, a film, which isidentical with the film composing the giant magnetoresistance element,is formed on the second wiring.

In a further preferred form of the present invention, more than half ofthe top surface and the side surface of the second wiring is coated withthe same film that forms the giant magnetoresistance element.

In a further preferred form of the present invention, the giantmagnetoresistance element is connected with the integrated circuitthrough a bonding wire.

In a further preferred form of the present invention, the giantmagnetoresistance element is formed by repeatedly laminating aFe(x)Co(1−x) layer (0≦×≦0.3) and a Cu layer, film thickness of the Culayers per layer being set to such a film thickness that causes thechange rate of magnetoresistance in a layer of the Cu layers to bearound the second peak, and protective films on the giantmagnetoresistance element is formed by spin coating or by means oflow-thermal plasma CVD method.

In a further preferred form of the present invention, a diode is formedbetween the giant magnetoresistance element and the integrated circuit.

In a further preferred form of the invention, mean surface roughness ofthe underlayer is 50 Å or less. In a further preferred form of theinvention, mean surface roughness of the underlayer is between 1 Å and25 Å.

In a further preferred form of the invention, further comprising adifferential amplifier and a comparator on a line for transmittingoutput of the giant magnetoresistance element to the integrated circuit,wherein the comparator sets the output of the differential amplifierbeing constant irrespective of the distance between the giantmagnetoresistance element and the object to be observed by the giantmagnetoresistance element, as the criterion for deciding the position ofan object to be observed.

In accordance with a yet further aspect of the present invention, thereis provided a magnetic field sensing device which comprises a magneticrotating body being rotatable about the rotation axis and having aconcavity and a convexity along its outer periphery, a magnet disposedso as to face the outer periphery of the magnetic rotating body and amagnetic field sensing element, which is attached to the magnet surfaceopposing the outer periphery of the magnetic rotating body, wherein themagnetic field sensing element detects a change in a magnetic fieldgenerated between the magnetic rotating body and the magnet during therotation of the magnetic rotating body, and wherein the device detects arotation amount of the magnetic rotating body on the basis of thedetected change in the magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the structure of a magnetic field sensingelement according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing the structure of the magnetic fieldsensing element according to Embodiment 1 of the present invention.

FIG. 3 is a side view showing the structure of the magnetic fieldsensing device according to Embodiment 1 of the present invention.

FIG. 4 is a perspective view showing the structure of the magnetic fieldsensing device according to Embodiment 1 of the present invention.

FIG. 5 is a block diagram schematically showing the internal structureof a magnetic field sensing device according to Embodiment 1 of thepresent invention.

FIG. 6 is a graph showing the characteristics of the relationshipbetween the rate of change in resistance per unit of magnetic field andthe surface roughness of the underlayer of the magnetic field sensingelement of the present invention.

FIG. 7 is a conceptual view showing the manufacturing process of themagnetic field sensing element according to Embodiment 1 of the presentinvention.

FIG. 8 is a conceptual view showing the manufacturing process of themagnetic field sensing element according to Embodiment 1 of the presentinvention.

FIG. 9 is a conceptual view showing the manufacturing process of themagnetic field sensing element according to Embodiment 1 of the presentinvention.

FIG. 10 is a conceptual view showing the manufacturing process of themagnetic field sensing element according to Embodiment 1 of the presentinvention.

FIG. 11 is a partial sectional view of a magnetic field sensing elementaccording to Embodiment 2 of the present invention.

FIG. 12 is a partial sectional view of the magnetic field sensingelement according to Embodiment 2 of the present invention.

FIG. 13 is a sectional view conceptually showing the manufacturingprocess of a magnetic field sensing element according to Embodiment 3 ofthe present invention.

FIG. 14 is a sectional view conceptually showing the manufacturingprocess of the magnetic field sensing element according to Embodiment 3of the present invention.

FIG. 15 is a sectional view conceptually showing the magnetic fieldsensing element according to Embodiment 3 of the present invention.

FIG. 16 shows an essential portion of a magnetic field sensing elementaccording to Embodiment 4 of the present invention.

FIG. 17 is a side view showing the structure of a magnetic field sensingdevice according to Embodiment 5 of the present invention.

FIG. 18 is a perspective view showing the structure of the magneticfield sensing device according to Embodiment 5 of the present invention.

FIG. 19 is a conceptual view showing the structure in section during amanufacturing process of the magnetic field sensing element according toEmbodiment 5 of the present invention.

FIG. 20 is a conceptual view showing the structure in section during amanufacturing process of the magnetic field sensing element according toEmbodiment 5 of the present invention.

FIG. 21 is a conceptual view showing the structure in section during amanufacturing process of the magnetic field sensing element according toEmbodiment 5 of the present invention.

FIG. 22 is a conceptual view showing the structure in section of amagnetic field sensing element according to Embodiment 6 of the presentinvention.

FIG. 23 is a conceptual view showing the structure in section of themagnetic field sensing element according to Embodiment 6 of the presentinvention.

FIG. 24 shows the structure of the front surface of a magnetic fieldsensing element according to Embodiment 7 of the present invention.

FIG. 25 shows the structure of the rear surface of the magnetic fieldsensing element according to Embodiment 7 of the present invention.

FIG. 26 is a perspective view of the magnetic field sensing elementaccording to Embodiment 7 of the present invention.

FIG. 27 is a side view of the magnetic field sensing element accordingto Embodiment 7 of the present invention.

FIG. 28 shows the structure of the front surface of a magnetic fieldsensing element according to Embodiment 8 of the present invention.

FIG. 29 shows the structure of the rear surface of the magnetic fieldsensing element according to Embodiment 8 of the present invention.

FIG. 30 is a perspective view of the magnetic field sensing elementaccording to Embodiment 8 of the present invention.

FIG. 31 is a side view of the magnetic field sensing element accordingto Embodiment 8 of the present invention.

FIG. 32 is a block diagram conceptually showing the structure of amagnetic field sensing device according to Embodiment 8 of the presentinvention.

FIG. 33 is a graph showing operating characteristics of the magneticfield sensing element according to Embodiment 8 of the presentinvention.

FIG. 34 is a side view showing the structure of a conventional magneticfield sensing device.

FIG. 35 is a perspective view showing the structure of the conventionalmagnetic field sensing device.

FIG. 36 is a graph showing the characteristics of a conventional GMRelement.

FIG. 37 is a side view showing the structure of a magnetic field sensingdevice using a conventional GMR element.

FIG. 38 is a perspective view showing the structure of the magneticfield sensing device using the conventional GMR element.

FIG. 39 is a block diagram showing the magnetic field sensing deviceusing the conventional GMR element.

FIG. 40 is a block diagram showing the detail of the magnetic fieldsensing device using the conventional GMR element.

FIG. 41 shows an example of the structure of a circuit of the magneticfield sensing device using the conventional GMR element.

FIG. 42 shows the structure of the conventional magnetic field sensingelement.

FIG. 43 is a graph showing operating characteristics of the conventionalmagnetic field sensing element.

FIG. 44 is a top view transparently showing the structure of themagnetic field sensing element according to Embodiment 1.

FIG. 45 is a sectional view showing the structure of the magnetic fieldsensing element cut along line A-A′ in FIG. 44.

FIG. 46 is a top view transparently showing the structure of a magneticfield sensing element according to Embodiment 9.

FIG. 47 is a sectional view showing the structure of the magnetic fieldsensing element cut along line A-A′ in FIG. 46.

FIG. 48 is a plan view showing the structure of the magnetic fieldsensing element according to Embodiment 9.

FIG. 49 is a sectional view showing the structure of the magnetic fieldsensing element cut along line B-B′ in FIG. 48.

FIG. 50 is a sectional view showing the structure of the magnetic fieldsensing element according to Embodiment 9.

FIGS. 51 is a top view transparently showing the structure of a magneticfield sensing element according to Embodiment 10.

FIGS. 52 is a sectional view showing the structure of the magnetic fieldsensing element according to Embodiment 10.

FIG. 53 is a graph showing a heat resisting characteristic of a GMRelement used in a magnetic field sensing element according to Embodiment11.

FIG. 54 is a block diagram conceptually showing the structure of amagnetic field sensing element according to Embodiment 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a magnetic field sensing element according tothe present invention will now be described, while referring to theaccompanying drawings.

Embodiment 1

FIG. 1 is a plan view showing the structure of a magnetic field sensingelement according to Embodiment 1 of the present invention. FIG. 2 is asectional view taken along the line A—A of FIG. 1. FIGS. 3 and 4 are aside view and a perspective view, respectively, showing the structure ofa magnetic field sensing device according to Embodiment 1 of the presentinvention. FIG. 5 is a block diagram schematically showing the internalstructure of the magnetic field sensing device according to Embodiment 1of the present invention.

As shown in FIGS. 1 and 2, a magnetic field sensing element 28 accordingto Embodiment 1 of the present invention comprises metal wiring 6 asfirst wiring and a GMR element 7 on an underlayer 2 formed on asubstrate 1.

As shown in FIGS. 3 and 4, the magnetic field sensing device comprises amagnetic rotating body 30 which has at least one concavity and convexityalong its outer periphery and which rotates synchronously with therotation of a rotation axis 29, a magnetic field sensing element 28arranged so as to face the outer periphery of the magnetic rotating body30 with a predetermined gap therebetween, a magnet 31 for applying amagnetic field to a GMR element 7 of the magnetic field sensing element28, and an integrated circuit 3 for processing output of the GMR element7.

In Embodiment 1, the GMR element is formed on the same surface theintegrated circuit is formed.

As described above, since the GMR element is formed of a super thin filmlayer with a thickness of several Å to several dozen Å, it is liable tobe effected by subtle unevenness of the surface of the underlayer onwhich the GMR element is arranged.

When the unevenness of the surface of the underlayer is considerable,the GMR element does not show any change in resistance.

As the surface of the underlayer becomes smoother, the rate of change inresistance of the GMR element becomes larger. However, the magneticfield for generating the change in resistance is required to be largeraccordingly.

FIG. 6 is a graph showing the characteristics of the relationshipbetween the rate of change in resistance per unit magnetic field and thesurface roughness of the underlayer of the magnetic field sensingelement.

The rate of change in resistance per unit magnetic field (hereinafterreferred to as the magnetic field sensitivity) shown in FIG. 6 showscharacteristics in the case where, as a substrate on which a GMR elementis arranged, a substrate on which an underlayer of Si, an Si thermaloxide film, silicon oxide, silicon nitride, tantalum oxide or the likeis formed by sputtering, a soda glass substrate, and various kinds ofceramic substrates are used.

The smoothness of the surface of the underlayer can be measured by usingAFM (Atomic Force Microscope) or the like. In FIG. 6, the smoothness isrepresented by the mean roughness (Ra).

As can be seen in FIG. 6, a large magnetic field sensitivity of the GMRelement can be obtained when the average of surface roughness Ra is 50 Åor less, and in particular, the best magnetic field sensitivity can beobtained when the average of surface roughness Ra is 1 Å or more and 25Å or less.

Further, the GMR element is electrically connected with the integratedcircuit by a metal film formed in the process of forming the integratedcircuit. In the integrated circuit, elements such as a transistor and aresistance are electrically connected by a metal film generally composedof an aluminum film. The GMR element is electrically connected with theintegrated circuit by forming this aluminum film in a predeterminedregion necessary for connecting the GMR element with the integratedcircuit.

The patterning process in which the wiring is formed from this aluminumfilm is carried out by wet etching. The wiring can have a tapered shapein section by utilizing the characteristics of isotropic etching by wetetching, and thus, the connecting portion between the GMR element andthe aluminum film can have a shape that is advantageous in terms ofstrength.

FIG. 44 is a top view transparently showing the structure of themagnetic field sensing element according to Embodiment 1.

A GMR element 7 shown in FIG. 44 is represented, in a manner unlike therepresentation way of the GMR element 7 in FIG. 1, by more thick lines.However, these two figures show the GMR elements having the samestructure.

FIG. 45 is a sectional view showing the structure of the magnetic fieldsensing element cut along line A-A′ in FIG. 44.

As shown in FIGS. 44 and 45, in Embodiment 1 of the present invention, aGMR element film 5 b may be formed on the metal wiring 6. Incidentally,FIG. 45 shows a state in which protective films 108 and 109 are furtherformed on the GMR element film 5 b.

In this way, when the GMR element film 5 b is patterned to be formed onthe metal wiring 6, electrical connection between the metal wiring 6 andthe GMR element film 5 b can be ensured.

Though it is preferable in this case that all of the top surface and theside surface of the metal wiring 6 are coated with the GMR element film5 b, sufficient effect would be obtained if coating more than about halfof the top surface and the side surface of the metal wiring 6 arecoated.

FIGS. 7 to 10 are conceptual views showing the manufacturing process ofthe magnetic field sensing element according to Embodiment 1 of thepresent invention.

First, as shown in FIG. 7, in the process of forming the integratedcircuit of the magnetic field sensing element 28, a metal film 4, suchas an aluminum film, is formed on the surface of the underlayer 2 of anSi thermal oxide film or the like formed on the substrate 1, forexample, an Si substrate. Then, when the integrated circuit 3 is formed,a portion of the metal film 4 without the integrated circuit formedthereon (the right half on the substrate 1) remains unpatterned.

Then, as shown in FIG. 8, the metal film 4 is patterned intopredetermined metal wiring 6 utilizing photolithographic transfer.

Thereafter, as shown in FIG. 9, a GMR element film 5 is formed on theentire surface, and, as shown in FIG. 10, the GMR element 7 is patternedutilizing the photolithographic transfer.

In this way, in Embodiment 1, the GMR element 7 is formed on theunderlayer 2 formed on the substrate 1, and further, a portion of themetal film 4 for forming the integrated circuit 3 is used as the metalwiring 6 for electrically connecting the integrated circuit 3 with theGMR element 7. Therefore, unlike the conventional case, it is notnecessary to electrically connect a GMR element formed on a film surfaceand an integrated circuit formed on another film surface, and it is notnecessary to newly form a metal film for forming the wiring.Accordingly, higher productivity and lower cost of a magnetic fieldsensing element 28 and a magnetic field sensing device using themagnetic field sensing element can be attained.

Further, since mean surface roughness of the underlayer 2 on which theGMR element 7 is formed, is made to be 50 Å or less, and preferably,between 1 Å and 25 Å, the characteristics of the GMR element 7 can beimproved, and a highly accurate magnetic field sensing element can beprovided.

Further, since the metal film 4 at the connecting portion between themetal wiring 6 and the GMR element 7 can be made with a tapered shape insection by using wet etching to carry out the patterning process forforming the metal wiring 6 from the metal film 4, breakage at theconnecting portion is considerably inhibited, and thus, the reliabilityof the magnetic field sensing element 28 and a magnetic field sensingdevice using the magnetic field sensing element 28 can be improved.

Embodiment 2

In Embodiment 1, the metal wiring 6 can be satisfactorily connected withthe GMR element 7 by forming the GMR element film 5 as a giantmagnetoresistance element on the patterned metal film (i.e., the metalwiring 6 shown in FIG. 10) and on the underlayer 2 (see FIGS. 8 and 9)and patterning the GMR element film 5.

However, the thickness of the GMR element 7 is about 500 Å-2000, whichis relatively thinner than the metal film 4 forming the metal wiring 6,and thus, if the metal film 4 is sufficiently thicker than the GMRelement 7, the connection at the connecting portion between the metalwiring 6 and the GMR element 7 may become unstable. This is because theGMR element 7, which is thinner than the metal film 4 forming the metalwiring 6, may break due to a large difference in their levels at theconnecting portion.

In this case, a sufficient connection can be obtained by making therespective surfaces on which the metal wiring 6 and the GMR element 7are formed substantially the same height. A description of such methodwill be made below. FIGS. 11 and 12 are partially sectional views of amagnetic field sensing element according to Embodiment 2 of the presentinvention.

Suppose that, for instance, the thickness of the metal film 4 is 1 μm.As shown in FIG. 11, an Si oxide film 8 with a thickness of 1.5 μm isformed, as a first level difference buffer layer, on the metal wiring 6,formed by patterning the metal film 4, and on the underlayer 2.

Then, the surface of the Si oxide film 8 is polished with ultrafineparticles, diamond particles and the like. When the thickness to bepolished away is a little more than 1.5 μm, the difference in the levelsbetween the surface of the Si oxide film 8 and the surface of the metalfilm 4 for forming the metal wiring 6 can be made sufficiently smallerthan the film thickness of the GMR element 7, and thus, as can be seenfrom the sectional view after polishing in FIG. 12, the surfaces of themetal wiring 6 and the Si oxide film 8 can be made flush.

If the GMR element 9 is formed on the metal wiring 6 and the Si oxidefilm 8 after making their surfaces flush in the above way, there is nodifference in the level between the metal wiring 6 and the GMR element 9at the connecting portion, and thus, the connection state can beimproved. It is to be noted that, since the abrasive grains used forpolishing the Si oxide film 8 are sufficiently fine, the surface afterpolishing is sufficiently smooth and satisfactory GMR elementcharacteristics can be obtained.

Above description, a case is described where the Si oxide film 8 isused. However,when an insulating layer of tantalum oxide, siliconnitride, or the like is used, the same effect as above description canbe obtained.

Embodiment 3

FIGS. 13 and 14 are sectional views conceptually showing themanufacturing process of a magnetic field sensing element according toEmbodiment 3 of the present invention.

FIG. 15 is a sectional view conceptually showing the magnetic fieldsensing element according to Embodiment 3 of the present invention.

In Embodiment 3, by applying a resist or a resin layer of polyimide,PVSQ (silicon ladder polymer), or the like as a first level differencebuffer layer by spin coating, the surface on which the surface on whichthe wiring is formed and the surface on which the GMR element is formedare made flush.

For example, similar to Embodiment 2, when, a resist 10 with a thicknessof 2 μm is applied onto the entire surface by spin coating after themetal film with a thickness of 1 μm has been patterned to form the metalwiring 6, the surface of the resist 10 becomes flat without a leveldifference as shown in FIG. 13.

Then, the surface of the resist 10 is removed by resist ashing and thelike to evenly thin the resist 10. By removing the resist 10 until theupper surface of the metal wiring. 6 appears, the difference of thelevel between the surface of the resist 10 and the surface of the metalfilm 4 for forming the metal wiring 6 can be made sufficiently smallerthan the film thickness of the GMR element 9 as shown in FIG. 14, andthe upper surface of the metal wiring 6 with the surface on which theGMR element 9 is formed can thereby be made substantially flush insection after the resist ashing.

A thin film such as an Si oxide film with a thickness of 1,000 Å, forinstance, is formed on the entire upper surface of the above formedmetal wiring 6 and the resist 10, and the thin film formed on the metalwiring 6 is removed by photolithography and RIE (reactive ion etching)to leave only an Si oxide film 11 on the resist 10 and expose the metalwiring 6 (see FIG. 15).

The rest of the process forming the GMR element 9 comprises similar toEmbodiment 2, as shown in FIG. 15.

In the above description, resist ashing is used as the method ofthinning the resist 10. However, RIE (reactive ion etching), IBE (ionbeam etching), wet etching using an etchant or the like can remove theresist in a way similar to above case.

Further, since the resist is easily effected by a solvent or the like,the Si oxide film 11 with a thickness of 1,000 Å is formed on the resist10 before the GMR element 9 is formed, to prevent the resist 10 frombeing removed when the GMR element 9 is patterned.

It is to be noted that, if a solvent that is not capable of dissolvingthe resist layer is used in the process of patterning the GMR element 9,the above mentioned Si oxide film need not be formed.

Embodiment 4

FIG. 16 shows an essential portion of a magnetic field sensing elementaccording to Embodiment 4 of the present invention.

In Embodiment 4, after the GMR element film 5 as a giantmagnetoresistance element is formed on the entire upper surface of theunderlayer 2 and the metal wiring 6, a GMR element film 5 a formed onthe integrated circuit is left unremoved and the GMR element 7 ispatterned.

This type of patterning of the GMR element 7 is generally carried out byIBE. Accordingly, if, as in Embodiment 1, only the portion to be used asthe GMR element 7 is left and the patterning is carried out, and theother portions are removed, ion collisions may damage the integratedcircuit. However, in Embodiment 4, since the GMR element on theintegrated circuit is not removed when the GMR element 7 is patterned,the integrated circuit can be protected from damage due to ioncollisions. As a result, the reliability of the magnetic field sensingelement can be improved.

Embodiment 5

FIGS. 17 and 18 are a side view and a perspective view, respectively,showing the structure of a magnetic field sensing device according toEmbodiment 5 of the present invention.

In Embodiment 5, as shown in FIGS. 17 and 18, the GMR element 9 as agiant magnetoresistance element is formed on the integrated circuit 3.

FIGS. 19, 20, and 21 are conceptual views showing the structure insection during a manufacturing process of a magnetic field sensingelement used in the magnetic field sensing device according toEmbodiment 5 of the present invention.

As shown in FIG. 19, the integrated circuit 3, metal pads 11, and theunderlayer 2 are formed on the substrate 1 by photolithographic transferand RIE. Further, an Si oxide film 36 as a second level differencebuffer layer is formed on the entire exposed upper surfaces of the metalpads 11 and the upper surface of the underlayer 2.

The Si oxide film 36 must be formed thicker than the maximum leveldifference d between the surfaces of the underlayer 2 and the surface ofthe metal pads 11 (see arrows in FIG. 19). For example, the Si oxidefilm 36 is about twice as thick as the maximum level difference d. Thesurface of the Si oxide film 36 is polished smooth in a way similar toEmbodiment 2.

Here, the thickness of the Si oxide film 36 to be polished away is alittle less than the maximum level difference d of the integratedcircuit 3.

It is to be noted that, though FIGS. 19 to 21 show a portion where themetal pads 11 are formed directly on the integrated circuit 3, there isalso a portion where the metal pads 11 are formed on the underlayer 2which is an insulating layer, thus insulating the metal pads 11 and theintegrated circuit 3.

After polishing is carried out as shown in FIG. 20, only the Si oxidefilm 36 on the metal pads 11 is removed by photolithographic transferand RIE to form holes 13 above the metal pads 11 (FIG. 21 shows a statewhere the holes 13 are filled with a metal film 12). Then, the metalfilm 12 is formed in the holes 13 and on the entire upper surface of theSi oxide film 36. The thickness of the metal film 12 is a little morethan the depth of the holes 13.

Further, after photolithographic transfer is conducted, by etching themetal film 12, only the metal film 12 formed on the Si oxide film 36 isremoved to leave the metal film 12 only inside the holes 13, and theholes 13.

Here, the level difference which existed between the surface of theunderlayer 2 and the surface of the metal pads 11 (see FIG. 19) does notexist on the Si oxide film 36, and thus, the Si oxide film 36 having asurface that is sufficiently smooth for forming the GMR element 9thereon can be formed.

Then, as shown in FIG. 21, when the GMR element 9 is formed so as to beconnected with the metal film 12 embedded in the holes 13,not only canthe GMR element 9 be formed above the integrated circuit 3, but theintegrated circuit 3 can also be electrically connected with the GMRelement 9.

Since this makes it possible to reduce the area of the substrate 1, notonly can the cost be lowered, but also a magnetic field sensing element32 and a magnetic field sensing device using the magnetic field sensingelement 32 can be miniaturized.

It is to be noted that since there is generally a level difference onthe surface of the integrated circuit 3 and the GMR element 9 isstrongly affected by even a subtle level difference on the surface ofthe underlayer 2, this level difference is eliminated before the GMRelement 9 is formed.

Embodiment 6

FIGS. 22 and 23 conceptually show the structure in section of a magneticfield sensing element according to Embodiment 6 of the presentinvention.

In Embodiment 6, instead of the Si oxide film used in Embodiment 5,resist is used as a second level difference buffer layer to form amagnetic field sensing element.

As shown in FIG. 22, after the integrated circuit 3 is formed on thesubstrate 1, the metal pads 11 for electrically connecting with theintegrated circuit 3 are formed, and resist 14 as the second leveldifference buffer layer is applied by spin coating to the exposedsurfaces of the metal pads 11 and the entire surface of the underlayer2. The thickness of the applied resist 14 is more than the maximum leveldifference d between the surface of the underlayer 2 and the surface ofthe metal pads 11. Here, for example, the resist 14 is formed so as tobe about twice as thick as the maximum level difference d of the surfaceof the integrated circuit 3.

As shown in FIG. 22, the surface of the resist 14 as the second bufferlayer is smooth. Further, an Si oxide film 15 with a thickness of, forexample, 1,000 Å is formed on the resist 14.

It is to be noted that, although the Si oxide film 15 is used here, afilm of some other appropriate material may be used.

Next, the Si oxide film 15 and the resist 14 on the metal pads 11 areremoved to form the holes 13 above the metal pads 11 byphotolithographic transfer, RIE, and resist ashing.

Since the resist 14 is easily dissolved in etchant used for forming theholes 13, the Si oxide film 15 is formed on the resist 14 to prevent theresist, except the portions for forming the holes 13 therein, from beingdissolved in the etching process. Therefore, if a solvent that does notdissolve the resist 14 is used in the etching process, the Si oxide film8 need not be formed.

Then, a metal film 16 is formed in the holes 13 and on the entiresurface of the Si oxide film 15. The thickness of the metal film 16 is alittle more than the depth of the holes 13 (this state is not shown).

Further, the metal film 16 except the portions above the metal pads 11is removed by photolithographic transfer and by etching.

As a result, as shown in FIG. 23, the holes 13 above the metal pads 11can be filled with the metal film 16.

The level difference which existed on the surface of the integratedcircuit 3 has been eliminated, and thus, a surface which is smoothenough for forming the GMR element 9 thereon can be obtained.

As shown in FIG. 23, the GMR element 9 can be formed over the integratedcircuit 3 by forming the GMR element 9 on the Si oxide film 15 so as tobe connected with the metal film 16 embedded in the resist 14 and the Sioxide film 15.

As a result, it possible to reduce the area of the substrate 1, andthus, not only can the cost be lowered, but a magnetic field sensingelement 33 and a magnetic field sensing device using the magnetic fieldsensing element 33 can also be miniaturized.

Further, although a resist is used above description, a resin layer ofpolyimide, PVSQ, or the like may be applied by spin coating to obtain asimilar effect.

Embodiment 7

FIGS. 24 and 25 show the structure of the front surface and the backsurface, respectively, of a magnetic field sensing element according toEmbodiment 7 of the present invention.

FIGS. 26 and 27 are a perspective view and a side view, respectively, ofthe magnetic field sensing element according to Embodiment 7 of thepresent invention.

In Embodiment 7, the GMR element 9 is formed on a different plane thanthe plane of the substrate where the integrated circuit is formed.

As shown in FIGS. 26 and 27, the substrate 1 on which the GMR element 9is formed is arranged on a substrate 17 as a second substrate such thatthe surface where the GMR element 9 is formed is covered by thesubstrate 17.

In this case, wiring 18 arranged on the substrate 17 is electricallyconnected via solder 37 with metal pads 19 on the surface where the GMRelement 9 of the substrate 1 is formed. Further, the metal pads 11 onthe surface where the integrated circuit 3 of the substrate 1 are formedis electrically connected via wires 20 with the wiring 18 on thesubstrate 17.

In this way, in Embodiment 7, since the GMR element 9 is formed on adifferent surface than the surface of the substrate 1 on which theintegrated circuit 3 is formed, and metal pads 19 for connection arefurther provided, the area of the substrate 1 can be reduced. Therefore,not only can a magnetic field sensing element 34 and a magnetic fieldsensing device using the magnetic field sensing element 34 beminiaturized, but the cost can also be lowered.

It is to be noted that, the substrate 1 is arranged so that the surfaceon which the GMR element 9 is formed is covered by the substrate 17.However, a similar effect can be obtained by arranging the substrate 1so that the surface on which the integrated circuit 3 is formed iscovered by the substrate 17.

Embodiment 8

FIGS. 28 and 29 are a front view and a rear view, respectively, whichshow a magnetic field sensing element according to Embodiment 8 of thepresent invention.

FIGS. 30 and 31 are a perspective view and a side view of the magneticfield sensing element according to Embodiment 8 of the presentinvention.

In Embodiment 8, a GMR element 9 is formed on both surfaces of thesubstrate 1. More specifically, a GMR element 9 is formed on theintegrated circuit 3 on the surface where the integrated circuit 3 isformed, similar to the case of Embodiment 5, and a GMR element 9 is alsoformed on the opposite surface. It is to be noted that the method offorming the GMR elements 9 and the like is similar to that in otherembodiments.

In this way, if a GMR element 9 is formed on both surfaces of thesubstrate 1, a highly accurate magnetic field sensing element can beobtained. Further, there are also advantages in the area of thesubstrate can be reduced, a low-cost magnetic field sensing element canbe obtained, and the magnetic field sensing element can be miniaturized.

FIG. 32 is a block diagram conceptually showing the structure of amagnetic field sensing device according to Embodiment 8 of the presentinvention.

FIG. 33 is a graph showing operating characteristics of the magneticfield sensing element according to Embodiment 8 of the presentinvention.

As shown in FIG. 32, the magnetic field sensing device according toEmbodiment 8 of the present invention is arranged with a predeterminedgap between a magnetic rotating body 21, and comprises a Wheatstonebridge circuit 23 using the GMR element 9 to which a magnetic field isapplied by a magnet 22, a differential amplification circuit 24 foramplifying the output of the Wheatstone bridge circuit 23, a comparisoncircuit 25 for comparing the output of the differential amplificationcircuit 24 with a reference value to output a signal of either “0” or“1,” and an output circuit 26 for switching in response to the output ofthe comparison circuit 25.

Since the structure of the circuit of the Wheatstone bridge circuit 23shown in FIG. 32 is similar to a conventional one (see FIG. 41), thedescription thereof is omitted.

In FIG. 32, rotation of the magnetic rotating body 21 causes a change inthe magnetic field supplied to the GMR element 9 forming the Wheatstonebridge circuit 23. Then, as shown in FIG. 33, output corresponding tothe concavities and the convexities of the magnetic rotating body 21 canbe obtained at an output end of the differential amplification circuit24.

Points A and B are output characteristics of the differentialamplification circuit with respect to the change in the gap between theGMR element 9 and the magnetic rotating body 21, where the output of thedifferential amplifier is constant irrespective of the gap.

Therefore, by setting the reference value of the comparison circuit soas to pass the points A and B, the output of the comparison circuit canbe changed at a predetermined position, irrespective of the gap amount,and thus, it is possible to make the gap characteristics satisfactory.Consequently, the amount of rotation of the magnetic rotating body 21can be accurately ascertained.

As described above, in Embodiment 8, since the GMR element 9 is formedon a surface which is not the surface on which the integrated circuit 3is formed, a highly accurate magnetic field sensing element 35 and amagnetic field sensing device using the magnetic field sensing element35 can be obtained. Further, since the area of the substrate can bereduced, the cost of the magnetic field sensing element can be lowered.Further, by reducing the area of the substrate, the magnetic fieldsensing element can be miniaturized.

It is to be noted that, although the structure where the GMR element 9is formed on the lower surface has been described, a similar effect canbe obtained by forming the integrated circuit on the lower surface.

Embodiment 9

FIGS. 46 to 50 are views showing the structure of a magnetic filedsensing element according to Embodiment 9.

Specifically, FIG. 46 is a top view transparently showing the structureof a magnetic field sensing element, FIG. 48 is a plan view showing thestructure of the magnetic field sensing element, FIGS. 47 and 49 aresectional views showing the structure of the magnetic field sensingelement cut along line A-A′in FIG. 46 and the line B-B′ in FIG. 48,respectively, and FIG. 50 is a sectional view showing the structure ofthe magnetic field sensing element according to Embodiment 9.

It is to be noted that a GMR element shown in FIG. 46 is, similar to theGMR element 7 shown in FIG. 44, represented in a manner different fromthe representation way of the GMR element 7 shown in FIG. 1. However,these figures show the GMR elements having the same structure.

As shown in FIG. 50, there is in general a level or height difference 3a on an integrated circuit 3, hence it is unsuitable to form a GMRelement on the integrated circuit 3. On the other hand, a flat surfacehaving almost no level difference exists on the top surface of anelectrode portion 3 b, which forms a capacitor 107, of the integratedcircuit 3.

The capacitor 107 is composed of the electrode portion 3 b as acapacitor portion of the integrated circuit 3 and an Si substrate 1sandwiching an insulating film 102 therebetween. A flat surface of arelative large area is provided on the top face of electrode portion 3b. This flat surface has sufficient flatness to form the GMR element 7thereon.

Consequently, when the GMR element 7 is formed on the electrode portion3 b of the integrated circuit 3, characteristics of the GMR element 7 isnot adversely affected.

Thus, a magnetic field sensing element 100 according to Embodiment 9 ofthe present invention is, similar to the magnetic field sensing elementdescribed in Embodiment 5, used for the magnetic field sensing devicesshown in FIGS. 17 and 18, in which, particularly according to Embodiment9, the GMR element 7 is formed on the electrode portion 3 b of theintegrated circuit 3.

To form the magnetic field sensing element 100 shown in FIG. 50,firstly, the insulating layer 102, the integrated circuit 3, anunderlayer 2 and a second metal layer 104 are formed on the substrate 1in the order stated. After forming a contact hole 101 in the secondmetal layer 104, a metal wiring 6 is connected to the second metal layer104 through the contact hole 101. Here, as described in Embodiment 1,the metal wiring 6 and the integrated circuit are formed of the metalfilm 4. The second metal layer 104 is used to electrically connect theintegrated circuit 3 to the GMR element 7 to be formed subsequently.

Then, the second metal layer 104 is patterned through thephotolithographic process and etching step to form a metal wiring 106 asthe second wiring. Thereafter, the GMR element 7 is formed on the metalwiring 106 and the underlayer 2.

The GMR element 7 is formed, after patterning the metal wiring 106, byforming a GMR element film 5 and a protective film 108 over the entiresurface of the metal wiring 106 and the underlayer 2 and patterning themutilizing the photolithographic technique.

Subsequently, after the GMR element 7 and the protective film 108 areformed, a protective film 109 is further formed to complete the magneticfield sensing element 100 having the structure shown in FIG. 50.

In the manufacturing method-of the magnetic field sensing element 100described above, the wet etching is preferably employed for thepatterning process to form the metal wiring 106 from the second metallayer 104. When utilizing isotropy of the wet etching, the metal wiring106 can have a tapered shape in section so that the connecting portionbetween the GMR element 7 and the metal wiring 106 has a sectional shapethat is advantageous in terms of strength.

As further shown in FIGS. 46 and 47, the GMR element film is patternedsuch that not only the connecting portion between the GMR element 7 andthe metal wiring 106 but the entire of the metal wiring is coated withthe GMR element film, which ensures the electrical connection betweenthe metal wiring 106 and the GMR element 7. Though it is preferable inthis case that all of the top surface and the side surface of the metalwiring 106 is coated with the GMR element film, sufficient electricalconnection between the metal wiring 106 and the GMR element 7 would bereliabled if coating more than about half of the top surface and theside surface of the metal wiring 106 is effected.

In the manufacturing method of the magnetic field sensing element 100mentioned above, a case is described in which the GMR element 7 isformed on the underlayer 2 that is formed on the electrode portion 3b ofthe integrated circuit 3. In the above description, the second metallayer 104 is patterned only as the metal wiring 106.

When the second metal layer-104 is patterned not only as the metalwiring 106 but also as a second integrated circuit (not shown), theunderlayer 2 functions as an interlayer insulating film between theintegrated circuit 3 and the second integrated circuit.

In this case where a part of the metal wiring 106 is also patterned asthe second integrated circuit, an interlayer insulating film (of thesame film quality as the underlayer 2) having the flat surface is formedon the electrode portion 3 b of the integrated circuit 3. Therefore, theGMR element 7 is appropriately formed on the interlayer insulating film.

As in the above magnetic field sensing element 100 according toEmbodiment 9 of the present invention, forming the GMR element 7 on theunderlayer 2 on the integrated circuit 3 makes the polishing processunnecessary which has otherwise been required to form a flat surface onwhich the GMR element 7 is formed, and makes it possible to reduce thearea of the substrate 1 as well. Therefore, it is expected to lower thecost and to miniaturize the magnetic field sensing element and hence themagnetic field sensing device using the same.

Embodiment 10

FIGS. 51 and 52 are a top view and a sectional view showing a magneticfield sensing element according to Embodiment 10 of the presentinvention.

Incidentally, a magnetic field sensing element 105 according toEmbodiment 10 of the present invention is used for the magnetic fieldsensing devices shown in FIGS. 17 and 18, similar to the magnetic fieldsensing element described in Embodiment 5.

As shown in FIG. 52, upon fabrication of the magnetic field sensingelement 105, similar to the manufacturing of the magnetic field sensingelement 100 in Embodiment 9 shown in FIG. 50, the metal wiring 6, theunderlayer 2 and the second metal layer 104 are sequentially formed onthe substrate and a GMR element is formed on the underlayer 2. However,the thickness of the underlayer 2 in Embodiment 10 is thicker than thatof in Embodiment 9.

The film thickness of the underlayer 2 is thus increased because theunderlayer 2 having a sufficient film thickness can provide through heattreatment a surface of sufficient flatness to form the GMR element 7even when the underlayer 2 is formed on the metal wiring 6.

By thickening the underlayer 2, on the other hand, it becomes difficultto electrically connect the metal wiring 6 with a metal wiring 106through a contact hole. This is because, while the contact hole can beformed, it is difficult to effectively fill in the contact hole thesecond metal layer 104 to be formed subsequently to the hole, with theresult that the electrical connection between the metal wiring 6 and themetal wiring 106 is not sufficiently reliabled.

Then, in the magnetic field sensing element 105 according to Embodiment10, holes 111 are formed through the underlayer 2, and the metal wiring106, formed by patterning the second metal layer through the holes 111,is connected to the metal wiring 6 by a bonding wire 103.

As shown in FIG. 52, the bonding wire 103 is connected between the GMRelement 7 and the metal wiring 6, thus the metal wiring 6 and the metalwiring 106 is connected through the GMR element 7 and bonding wire 103.Incidentally, the integrated circuit (not shown) is formed of the samealuminum film as the metal wiring 6.

In this way, when the underlayer 2 is formed thick, the metal wiring 6can be electrically connected to the metal wiring 106 through thebonding wire 103. With the underlayer 2 having the thus increasedthickness, a surface with sufficient flatness can be formed merelythrough a simple heat treatment such as reflow on the surface of theunderlayer 2 formed on the metal wiring 6.

Unlike the magnetic field sensing element 100 according to Embodiment 9,there is no need to take into consideration the level difference causedby the contact hole 101. Accordingly, in this embodiment, the metalwiring 106 can be formed with reduced thickness, whereas Embodiment 9requires the metal wiring to be formed thick in order to fill thecontact hole 101. As a result, the difference in film thickness betweenthe metal wiring 106 and the GMR element 7 can be decreased, therebymaking stable the electrical connection at the connecting portionbetween the metal wiring 106 and the GMR element 7.

Thus, the magnetic field sensing element 105 according to Embodiment 10of the present invention, a flat surface consitituting the GMR element 7can be formed by a simple flattening treatment such as heat treatment,so that the area of the substrate 1 may be reduced to miniaturize themagnetic field sensing element and hence the magnetic field sensingdevice using the same. In addition, the connecting condition between theGMR element 7 and the metal wiring 106 can be made more stable, loweringthe cost of fabrication thereof.

Embodiment 11

FIG. 53 is a graph showing characteristics in heat resistance of amagnetic field sensing element according to Embodiment 11 of the presentinvention.

In the graph shown in FIG. 53, the abscissa represents a substratetemperature at the formation of a protective film on the GMR element 7,and the ordinate represents the MR ratio (Magnetoresistance Ratio) ofthe GMR element 7. In Embodiment 11, a film obtained by repeatedlylaminating a Fe(x)Co(1−x) film (0 ≦×≦0.3) and a Cu film is used as theGMR element 7. The thickness of the Cu film per layer in this laminationbody is set to such a value(about 20 Å) that causes the MR ratio in onelayer of Cu to be around a second peak.

The graph in FIG. 53 shows that the MR ratio of the GMR element 7rapidly declines when heated above 300° C. in the substrate temperature.

The substrate temperature of the magnetic field sensing elementaccording to Embodiment 11 of the present invention is limited to 300°C. or lower at a step of forming protective films 108 and 109 on the GMRelement 7 comprising the Fe(x)Co(1−x) films (0≦×≦0.3) and the Cu filmslaminated one over the other.

In this case, as shown in FIG. 53, the characteristics of the GMRelement 7 rapidly declines when the substrate temperature exceeds 300°C. Since the GMR element 7 is a metal film comprising a so-calledartificial lattice in which magnetic layers and non-magnetic layers arelaminated alternately with a thickness of several angstroms to severaldozen angstroms, the protective films must be formed after formation ofthe GMR element 7 so as to reliable the corrosion resistance.

At the formation of these protective films, if the substrate temperatureis set to a temperature above 300° C., the characteristics of the GMRelement 7 rapidly declines as shown in FIG. 53. Therefore, theprotective films 108 and 109 are required to be formed by spattering orby means of cold or low temperature plasma CVD method which does notcause degradation in film quality of the GMR element 7.

When the protective films 108 and 109 are formed by spattering or bymeans of low temperature plasma CVD method, the substrate temperaturedoes not exceed 300° C., and hence deterioration in the characteristicsof the GMR element 7 can be avoided so the magnetic field sensingelement with a sufficient durability may be provided.

Embodiment 12

In the magnetic field sensing elements according to Embodiments 1 to 10,the GMR element 7 is patterned in general through the IBE(Ion BeamEtching) method.

Then, for instance, in the case, where GMR element film 5 is patternedso that only a portion used as the GMR element 7 is left unremoved as inEmbodiment 1, ion collisions generate the electric charge on the surfaceof the magnetic field sensing element. There is a fear that thiselectric charge may reaches the integrated circuit 3 through thesidewalls of the GMR element 7 to damage the integrated circuit 3.

FIG. 54 is a conceptual block diagram showing the structure of amagnetic field sensing element according to Embodiment 12.

The magnetic field sensing element according to Embodiment 12 isprovided with a protective diode 110 arranged between the integratedcircuit 3 and the GMR element 7. This protective diode 110 can preventthe electric charge from flowing into the integrated circuit 3 even ifthe surface of the GMR element 7 is electrified with the electric chargein the IBE process to pattern the GMR element 7. Incidentally, theprotective diode 110 can prevent the electric charge from flowing intothe integrated circuit 3 not only when the electric charge is generatedon the surface of the magnetic field sensing element during the IBEprocess mentioned above, but when, for instance, the electric charge isgenerated on the surface of the magnetic field sensing element duringother process such as the film formation process of the underlayer 2.

As a result, the integrated circuit 3 can be prevented from beingdamaged by the incoming electric charge, thus improving the reliabilityof the magnetic field sensing element.

According to the present invention, the following advantages can beobtained. Since a magnetic field sensing element comprises an underlayerformed on a substrate, a giant magnetoresistance element formed on theunderlayer for detecting a change in a magnetic field, and an integratedcircuit formed on the substrate for carrying out predeterminedarithmetic processing based on a change in a magnetic field detected bythe giant magnetoresistance element, and the giant magnetoresistanceelement and the integrated circuit are formed on the same surface, theproductivity of the magnetic field sensing element can be improved andthe cost can be lowered.

Further, since a metal film formed on the underlayer for forming theintegrated circuit, not in a region for forming the integrated circuit,is patterned to form wiring for connecting the giant magnetoresistanceelement and the integrated circuit, it is not necessary to form newwiring for connection. Accordingly, a magnetic field sensing elementwith low cost and good productivity can be formed.

Still further, since the wiring is formed by wet etching the metal filmand has a tapered shape in section, the metal film at the connectingportion of the GMR element has a tapered shape in section, and thus, thereliability of the connecting portion can be improved.

Still further, the reliability of the connecting portion can be improvedbecause a first level difference buffer layer is formed on theunderlayer in a region for forming the giant magnetoresistance elementto decrease a difference in the levels between the surface of the metalfilm for forming the wiring and a surface for forming the giantmagnetoresistance element, and the giant magnetoresistance element isformed on the first level difference buffer layer.

Still further, since the first level difference buffer layer is formedof an insulating layer, and the difference in the levels between thefirst level difference buffer layer and the surface of the metal filmfor forming the wiring is sufficiently smaller than the film thicknessof the giant magnetoresistance element, there is no level difference atthe connecting portion between the GMR element and the metal film, andthus, the reliability of the connecting portion can be improved.

Still further, since the first level difference buffer layer is a resistlayer or resin layer having fluid properties formed by spin coating, andthe difference in the levels between the first level difference bufferlayer and the surface of the metal film for forming the wiring issufficiently smaller than the film thickness of the giantmagnetoresistance element, there is no level difference at theconnecting portion between the GMR element and the metal film, and thus,the reliability of the connecting portion can be improved.

Still further, for the purpose of forming the giant magnetoresistanceelement, after a giant magnetoresistance element film is formed on theentire surface of the integrated circuit and the first wiring, a portionof the giant magnetoresistance element film on the first wiring thenbeing removed so that the giant magnetoresistance element film formed onthe integrated circuit is left unremoved, a protective film then beingformed on the unremoved portion of giant magnetoresistance element film,the integrated circuit is kept from being damaged by the patterning ofthe GMR element, and thus, the reliability of the magnetic field sensingelement can be improved.

Still further, since a magnetic field sensing element in anotherembodiment of the present invention comprises an integrated circuit, anunderlayer, and a metal pad formed on the substrate in the order stated,provided with a second level difference buffer layer formed on theunderlayer and the metal pads to absorb the difference of the levelsbetween the surface of the underlayer and the surface of the metal pads,and a giant magnetoresistance element formed on the second leveldifference buffer layer, the area of the substrate can be reduced, andthus, a low-cost magnetic field sensing element can be obtained.Further, there is an advantage in that the magnetic field sensingelement can be miniaturized.

Still further, since the second level difference buffer layer has asurface smoothed by polishing, and the giant magnetoresistance elementis formed on the smoothed surface of the second level difference bufferlayer, the GMR element is formed on the integrated circuit theunevenness of which is smoothed by the polishing process, and thus,there is an advantage in that a highly accurate magnetic field sensingelement can be obtained.

Still further, since the second level difference buffer layer is formedfrom a resist layer or resin layer having a smoothed surface formed byspin coating, and the giant magnetoresistance element is formed on thesmoothed resist layer or resin layer, there is an advantage in that ahighly accurate magnetic field sensing element can be obtained.

Still further, since a magnetic field sensing element in still anotherembodiment of the present invention comprises an underlayer formed onone surface of a substrate, a giant magnetoresistance element formed onthe underlayer for detecting a change in a magnetic field, and anintegrated circuit formed on the surface opposite to the surface wherethe giant magnetoresistance element of the substrate is formed forcarrying out predetermined arithmetic processing based on a change in amagnetic field detected by the giant magnetoresistance element, the areaof the substrate can be reduced, and thus, there is an advantage in thata low-cost magnetic field sensing element can be obtained. Further,there is an advantage in that the magnetic field sensing element can beminiaturized.

Still further, since an underlayer and a giant magnetoresistance elementare further formed on the integrated circuit formed on the oppositesurface of the substrate, there is an advantage in that a highlyaccurate magnetic field sensing element can be obtained. Further, thereare advantages in that the area of the substrate can be reduced, alow-cost magnetic field sensing element can be obtained, and themagnetic field sensing element can be miniaturized.

Still further, since a film, which is identical with the film composingthe giant magnetoresistance element, is formed on the first wiring, thefirst metal wiring can be electrically connected to the giantmagnetoresistance element in a reliable manner.

Still further, since more than half of the top surface and the sidesurface of the first wiring is coated with the same film that forms thegiant magnetoresistance element, better electrical connection can beobtained between the first metal wiring and the giant magnetoresistanceelement.

Still further, since a magnetic field sensing element comprising anintegrated circuit formed on a substrate and having a capasitor portion,an underlayer formed on the integrated circuit, a second metal layerformed on the underlayer, and a giant magnetoresistance element formedon the capacitor portion of the integrated circuit, the area of thesubstrate can be reduced without performing the flattening treatment toobtain the magnetic field sensing element at low cost. Also, themagnetic field sensing element can be miniaturized.

Still further, the giant magnetoresistance element is connected with theintegrated circuit through a second wiring formed by patterning thesecond metal layer, the thickness of the underlayer can advantageouslybe increased so that the area of the substrate can be reduced withoutperforming the flattening treatment other than heat treatment, and thefilm thickness of the second metal layer can advantageously be reducedso that the reliability of the connecting portion of the second metallayer to the giant magnetoresistance element can be improved. Also, themagnetic field sensing element can be miniaturized.

Still further, since a film, which is identical with the film composingthe giant magnetoresistance element, is formed on the second wiring,reliable electrical connection between the second wiring and the giantmagnetoresistance element can be ensured.

Still further, since more than half of the top surface and the sidesurface of the second wiring is coated with the same film that forms thegiant magnetoresistance element, better electrical connection can beobtained between the second wiring and the giant magnetoresistanceelement.

Still further, since the giant magnetoresistance element is connectedwith the integrated circuit through a bonding wire, sufficient flatnessto form the giant magnetoresistance element can be held by merely heattreating the underlayer without polishing the surface of the underlayer.

Still further, since the giant magnetoresistance element is formed byrepeatedly laminating a Fe(x)Co(1−x) layer (0≦×≦0.3) and a Cu layer,film thickness of the Cu layers per layer being set to such a filmthickness that causes the change rate of magnetoresistance in a layer ofthe Cu layers to be around the second peak, and since protective filmson the giant magnetoresistance element is formed by spin coating or bymeans of low-thermal plasma CVD method, sufficient durability can beensured in the magnetic field sensing element without degrading thecharacteristics of the GMR element.

Still further, since a diode is formed between the giantmagnetoresistance element and the integrated circuit, damage can beeliminated which may be done to the integrated circuit by the electriccharge in the electrified magnetic field sensing element in theformation step of the GMR element, and hence the magnetic field sensingelement with high reliability is provided.

Still further, since the average surface roughness of the underlayer is50 Å or less, there is an advantage in that a highly accurate magneticfield sensing element can be obtained.

Still further, since the average of the surface roughness of theunderlayer is between 1 Å and 25 Å, there is an advantage in that ahighly accurate magnetic field sensing element can be obtained.

Still further, since the magnetic field sensing element comprises adifferential amplifier and a comparator on a line for transmittingoutput of the giant magnetoresistance element to the integrated circuit,and since the comparator sets the output of the differential amplifierwhich is constant irrespective of the distance between the giantmagnetoresistance element and the object to be observed by the giantmagnetoresistance element, as the criterion for determining the positionof the object to be observed, there is an advantage in that a magneticfield sensing element with high accuracy can be obtained.

Further, a magnetic field sensing device is provided which comprises amagnetic rotating body being rotatable about the rotation axis andhaving a concavity and a convexity along its outer periphery, a magnetdisposed so as to face the outer periphery of the magnetic rotating bodyand a magnetic field sensing element, which is attached to the magnetsurface opposing the outer periphery of the magnetic rotating body,wherein the magnetic field sensing element detects a change in amagnetic field generated between the magnetic rotating body and themagnet during the rotation of the magnetic rotating body, and whereinthe device detects a rotation amount of the magnetic rotating body onthe basis of the detected change in the magnetic field. With thisarrangement, the productivity of the magnetic field sensing device canbe improved and the cost of fablication can be lowered.

What is claimed is:
 1. A magnetic field sensing element comprising: anunderlayer formed on a substrate; a giant magnetoresistance element fordetecting a change in a magnetic field; an integrated circuit formed onsaid underlayer for carrying out predetermined arithmetic processingbased on a change in a magnetic field detected by said giantmagnetoresistance element; a first wiring for connecting said giantmagnetoresistance element and said integrated circuit, said first wiringformed on said underlayer from a metal film for forming said integratedcircuit which is not in a region for forming said integrated circuit;and a first level difference buffer layer formed on said underlayer in aregion for forming said giant magnetoresistance element to decrease adifference in the levels between the surface of said first wiring and asurface for forming said giant magnetoresistance element, wherein saidgiant magnetoresistance element is formed on said first level differencebuffer layer.
 2. A magnetic field sensing element as claimed in claim 1,wherein said first wiring is formed by wet etching of said metal filmand has a tapered shape in section.
 3. A magnetic field sensing elementas claimed in claim 1, wherein said first level difference buffer layeris formed of an insulating layer, and the level difference between saidfirst level difference buffer layer and said surface of said metal filmfor forming said first wiring is sufficiently smaller than the filmthickness of said giant magnetoresistance element.
 4. A magnetic fieldsensing element as claimed in claim 3, wherein said first leveldifference buffer layer is a fluidized resist layer or resin layerhaving fluid properties formed by spin coating, and the level differencebetween said first level difference buffer layer and said surface ofsaid metal film for forming said first wiring is sufficiently smallerthan the film thickness of said giant magnetoresistance element.
 5. Amagnetic field sensing element as claimed in claim 1, wherein, for thepurpose of forming said giant magnetoresistance element, after a giantmagnetoresistance element film is formed on the entire surface of saidintegrated circuit and said first wiring, a portion of said giantmagnetoresistance element film on said first wiring then being removedso that the giant magnetoresistance element film formed on saidintegrated circuit is left unremoved, a protective film then beingformed on said unremoved portion of giant magnetoresistance elementfilm.
 6. A magnetic field sensing element comprising: an integratedcircuit, an underlayer, and a metal pad formed on a substrate in theorder stated; a level difference buffer layer formed on said underlayerand said metal pad to decrease a difference in levels between thesurface of said underlayer and the surface of said metal pad; and agiant magnetoresistance element formed on said level difference bufferlayer.
 7. A magnetic field sensing element as claimed in claim 6,wherein said level difference buffer layer has a surface that issmoothed by polishing, and said giant magnetoresistance element isformed on said smoothed surface of said level difference buffer layer.8. A magnetic field sensing element as claimed in claim 6, wherein saidlevel difference buffer layer is a resist layer or resin layer having asmoothed surface formed by spin coating and said giant magnetoresistanceelement is formed on said smoothed surface of said resist layer or resinlayer.
 9. A magnetic field sensing element comprising: a substrate; anunderlayer formed on a first surface of the substrate; a giantmagnetoresistance element formed on said underlayer, for detecting achange in a magnetic field; and an integrated circuit formed on a secondsurface of the substrate opposite to the first surface where said giantmagnetoresistance element of said substrate is formed, for carrying outpredetermined arithmetic processing based on a change in a magneticfield detected by said giant magnetoresistance element.
 10. A magneticfield sensing element as claimed in claim 9, wherein an underlayer and agiant magnetoresistance element are further formed on said integratedcircuit formed on the other surface of said substrate.
 11. A magneticfield sensing element as claimed in claim 1, wherein a film, which isidentical with the film composing said giant magnetoresistance element,is formed on said first wiring.
 12. A magnetic field sensing elementcomprising an integrated circuit formed on a substrate and having acapasitor portion, an underlayer formed on said integrated circuit, asecond metal layer formed on said underlayer, and a giantmagnetoresistance element formed on the capacitor portion of saidintegrated circuit.
 13. A magnetic field sensing element as claimed inclaim 12, wherein said giant magnetoresistance element is connected withsaid integrated circuit through a second wiring which is formed bypatterning said second metal layer.
 14. A magnetic field sensing elementas claimed in claim 12, wherein a film, which is identical with the filmcomposing said giant magnetoresistance element, is formed on said secondwiring.
 15. A magnetic field sensing element as claimed in claim 6,wherein said giant magnetoresistance element is connected with saidintegrated circuit through a bonding wire.
 16. A magnetic field sensingelement as claimed in claim 1, further comprising a diode formed betweensaid giant magnetoresistance element and said integrated circuit.
 17. Amagnetic field sensing element as claimed in claim 1, wherein meansurface roughness of said underlayer is 50 Å or less.
 18. A magneticfield sensing element as claimed in claim 1, further comprising adifferential amplifier and a comparator on a line for transmittingoutput of said giant magnetoresistance element to said integratedcircuit, wherein said comparator sets the output of said differentialamplifier, being constant irrespective of the distance between saidgiant magnetoresistance element and said object to be observed by saidgiant magnetoresistance element, as the criterion for determining theposition of an object to be observed.
 19. A magnetic field sensingdevice comprising: a magnetic rotating body being rotatable about therotation axis and having a concavity and a convexity along its outerperiphery; a magnet disposed so as to face the outer periphery of saidmagnetic rotating body; and a magnetic field sensing element as claimedin claim 1, which is attached to said magnet surface opposing the outerperiphery of said magnetic rotating body, wherein said magnetic fieldsensing element detects a change in a magnetic field generated betweensaid magnetic rotating body and said magnet during the rotation of saidmagnetic rotating body, and wherein said device detects a rotationamount of said magnetic rotating body on the basis of the detectedchange in the magnetic field.